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A self-consistent transport code is used to evaluate how plasma confinement in tokamaks is influenced by the microturbulent fields excited by the dissipative trapped electron (DTE) instability. The numerical results reproduce well the Neo-Alcator scaling law observed experimentally (for example in TEXTOR) in non-detached Ohmic discharges and the confinement degradation resulting when auxiliary heating is applied. The code results and the stability analysis lead to the following conclusions. The DTE instability is sufficient to explain the anomalous heat transport in low density discharges (attached plasmas) with or without additional heating; the marginal instability for the DTE mode thus follows from heat flux constraints. The observed marginal instability against the toroidal ion temperature gradient mode must then follow from particle flux constraints. The condition that both growth rates must be small is the restriction which determines the profiles that correspond to the experimental conditions and which determines, to a large extent, profile consistency. Finally, it is suggested that the deviation from Neo-Alcator scaling, the density limit and the phenomenon of plasma detachment are interrelated effects which arise at high densities, when the constraint on the electron heat flux becomes harder to satisfy.

Additional information

Authors: ROGISTER A, Kernforschungsanlage Julich GmbH (DE);HASSELBERG G, Kernforschungsanlage Julich GmbH (DE);WAELBROECK F G, Kernforschungsanlage Julich GmbH (DE);WEILAND J, Institute for Electromagnetic Field Theory, Chalmers University of Technology, Goteborg (SE)
Bibliographic Reference: Article: Nuclear Fusion, Vol.28 (1988), No.6, pp.1053-1073
Record Number: 198910228 / Last updated on: 1994-12-01
Original language: en
Available languages: en